1. Field of the Invention
The present invention relates to an ink jet recording equipment used in copy machine, facsimile, word processor, out put printer for host-computer, out put printer for VTR etc., particularly to an ink jet recording head in which ink-liquid-repellent treatment is applied at the discharging port (orifice) peripheral portion of the recording head used for said recording equipment, and to an ink jet recording equipment having said recording head.
2. Related Background Art
There has been known in the art an ink jet recording device which performs recording by discharging a recording liquid (ink) through a discharging port (orifice) of a recording head as a recording device excellent with respect to low noise, high speed recording, etc.
FIG. 1 shows a schematic perspective view for explaining the constitution of conventional ink jet recording head.
In this recording head, on a substrate 11 as a support formed of glass, ceramic or single crystal silicon substrate, a discharging energy-generating element 12 is located, and a liquid channel 15 and an orifice 14 corresponding to the discharging energy-generating element 12, and further a liquid chamber 16 are formed by patterning of a cured photosensitive resin film 13 according to photolithography. On the cured photosensitive resin film 13, a ceiling plate 17 formed of, for example, glass, ceramic, metal, resin, etc. is laminated and secured with an adhesive 19. Also, a recording liquid feeding opening 18 is formed at its ceiling plate 17.
In the recording head with such constitution, the physical properties (physical characteristics) of the surfaces of the substrate 11, the cured photosensitive resin film 13 and the ceiling plate 17 surrounding the orifice 14 are extremely important in permitting the recording liquid to be discharged constantly stably for performing record. More specifically, if the recording liquid comes around the outer surface portion of the orifice 14 (orifice peripheral portion) to form a liquid pool at a part thereof, the recording liquid in the liquid channel 15 when discharged through the orifice 14 will come out in its flying direction from the normal predetermined direction, and further due to unstable state of the liquid pool, its flying direction will be disturbed every time of discharging, whereby no stable liquid discharging can be effected to reach the limit improving recording quality.
Further, if the outer surface portion as a whole of the orifice 14 is covered with the film of the recording liquid, the so called splash phenomenon occurs to cause scattering of the recording liquid, whereby good recording can not be performed. Also, if the liquid pool covering over the outer surface portion of the orifice becomes greater, liquid discharging per se through the recording head may sometimes become impossible.
FIG. 1 shows one example of recording head preferably to good recording. In this recording head, as the members surrounding the orifice, there have been frequently used different materials such as silicon (substrate 11), glass (ceiling plate 17), resin (cured photosensitive resin film 13). The present inventors have found that the recording liquid will be leaked through the portion of the material most readily leakable among the three kinds of materials in the vicinity of the orifice by searching fully discharing of recording liquid at such recording head. For example, it has been found that since glass is the lowest in surface tension among the three kinds of materials as mentioned above relative to conventional ink (recording liquid), ink will be leaked through that portion.
As described above, in the recording head, if liquid pooling occurs at the peripheral portion of orifice, no stable discharging can be effected. This tendency is exhibited very markedly in performing high precision recording by increasing the nozzle density or in aiming at driving at high frequency, namely high speed recording. In other words, this tendency is a technical problem to improve more performance of the recording head when high speed and high quality recording is desired.
Accordingly, as shown in FIG. 2, a large number of proposals have been made to solve the above problem by applying the so called ink-liquid-repellent surface treatment (water-repellent treatment for aqueous ink and oil-repellent treatment for oily ink) on at least the peripheral portion of the orifice 14 to form a water-repelling treated layer 20 which repels ink. As the water-repellent treating agent to be used for the water-repellent treatment, for example, various silicone oils have been included. By the present inventors' knowledge, it is necessary to consider the relationship between a recording head and a recording equipment having the abovementioned recording head in order to perform record by use of the abovementioned recording head.
The surface treatment layer 20 to be formed on the ink jet recording head cannot be practical, unless it is not only good in ink-liquid-repellency but also sufficient in durability of the surface treatment layer in carrying out conventional ink jet recording. In the following, its durability is to be described.
When practicing the ink jet recording method, even if ink-liquid-repellent treatment may be applied at the orifice peripheral portion, for performing good discharging, the restoration operation of wiping the orifice surface with an absorbing material such as polyurethane foam, etc. to absorb the ink attached thereon is frequently done. Accordingly, the surface treatment layer is required to have adhesion to the extent that it will not be peeled off even when rubbed with an absorbing material and abrasion resistance, etc. to the extent that the layer will not be broken. If these durabilities are insufficient, although the ink-liquid-repellent effect may be exhibited at the initial stage, in the course of use of the head, the ink-liquid-repellent treated layer will be gradually peeled off or dropped off, until no ink-liquid-repellent effect can be exhibited and no stable discharging printing can be done.
With regard to such durability required for the ink jet recording head, there are many problems to be improved in order to enhance recording quality.
As shown in the ink jet head of FIG. 1 in the case that members forming the orifice are composed of a plurality of different materials, a surface treatment layer capable of keeping good adhesion to all materials of them, especially even in long period recording, must be formed. The surface treatment layer formed with the surface-treating agent of the prior art has yet room for improvement in this point.
The inventors has searched a surface-treating agent of ink-liquid-repellency. As the result, the surface-treating agents of the following composition are used for surface-treatment of ink-liquid-repellency for the recording head.
(a) A UV-ray polymerization curable composition containing a fluorine type polymer with an average molecular weight of 2,000 or more which is substantially insoluble in water and soluble in organic solvent and a polyfunctional monomer or a polyfunctional oligomer having two or more (meth)acryloyl groups in the molecule.
(b) A compound having at least one reactive group selected from the group consisting of fluoroalkyl groups, fluoroallyl groups, fluorocycloalkyl groups, fluoroalkallyl groups and fluoroalkylallyl groups and a silazane group.
For example, when the surface treatment of the above head (the substrate 11 of silicon, the ceiling plate 17 of glass, the cured resin film 13) is effected by the composition described in (a) or (b), a surface treatment layer improved in durability as compared with the case of using the surface-treating agent of the prior art was obtained.
The present inventors further have continued many experiments. As the result, it has been found that, even by use of the composition described in (a), ink-liquid-repellent effect reduces after use for a long period by peeling off of the agent.
It is assumed that this matter is caused by that the composition described in (a) exhibits particularly excellent adhesion to the organic material portion of the cured photosensitive resin film, but is not still unsatisfactory in adhesion to inorganic material portions such as glass and silicon.
On the other hand, even by use of the composition described in (b), the agent of (b) peals off after use for a long period in the similar manner to that in the composition (a).
It is assumed that the reasons for this phenomenon is reversed. That is to say, the composition described in (b) exhibits particularly excellent adhesion to glass and silicon, but is still insufficient in adhesion to organic material portion such as resin.
The ink jet recording head having the constitution as previously shown as a suitable embodiment is constituted of plural kinds of organic and inorganic materials from aspects of manufacturing, performance, cost, etc. Accordingly, there is further room for improvement of the above (a) and (b) with respect to practical performance of adhesion to both organic and inorganic materials.